San Antonio Orthopaedic Group, San Antonio, TX, USA.
Clin Orthop Relat Res. 2014 Jul;472(7):2144-50. doi: 10.1007/s11999-014-3672-0.
Monopolar and bipolar radial head prosthetic arthroplasties have been used successfully to treat elbow fracture-dislocation with unsalvageable radial head fractures. The relative stability of these two designs in different clinical situations is a topic of ongoing investigation.
QUESTIONS/PURPOSES: We tested the effects of monopolar and bipolar fixed-neck prosthetic radial head implants on improvement in elbow coronal and axial plane laxity in a terrible triad biomechanical model that accounted for lateral collateral ligament integrity and the presence of a transverse coronoid fracture.
Kinematic data were collected on six fresh-frozen cadaveric upper extremities tested with passive motion throughout the flexion arc. Varus and valgus gravity stress were applied with the wrist in neutral position. A lateral collateral ligament reconstruction was simulated. We assessed instability after radial head resection and reconstruction with either a monopolar or bipolar implant in the presence of a transversely fractured (Regan and Morrey Type 2) or fixed coronoid process.
With collateral ligament integrity, no difference was detected, with the numbers available, in valgus laxity between implants under valgus stress (p = 1.0). Laxity improvement with each prosthesis was higher when the coronoid was fractured (mean ± SD: monopolar: 7.4° ± 1.6°, p < 0.001; bipolar: 6.4° ± 1.6°, p = 0.003) than when it was fixed (monopolar: 4.0° ± 1.6°, p = 0.02; bipolar: 4.2° ± 1.6°, p = 0.01). With the numbers available, there was no difference in external rotation laxity between implants under valgus stress (p = 1.0). The greatest stabilizing effect of the prostheses occurred when the coronoid was fractured (monopolar: 3.3° ± 1.2°, p = 0.15; bipolar: 3.3° ± 1.2°, p = 0.17). Radial head arthroplasty offered no substantial stability under varus stress for varus or internal rotation laxity.
In our terrible triad cadaveric model, coronoid fixation was effective in improving varus laxity with a monopolar or bipolar prosthesis in place. Also, both types of prostheses were effective in improving valgus and external rotation laxity to the elbow, regardless of coronoid status. With collateral ligaments reconstructed, no large kinematic differences were noted between implants regardless of the varus-valgus position or whether the coronoid was fractured or fixed.
The data from our cadaveric model support the use of either implant type in terrible triad injuries if the collateral ligaments are intact or reconstructed.
单极和双极桡骨小头假体置换术已成功用于治疗不可挽救的桡骨小头骨折的肘关节骨折脱位。这两种设计在不同临床情况下的相对稳定性是一个正在研究的课题。
问题/目的：我们在一个考虑到外侧副韧带完整性和横向冠状突骨折的三联征生物力学模型中，测试了单极和双极固定颈假体桡骨小头植入物对改善冠状面和轴向松弛的影响。
对六具冷冻尸体上肢进行了运动学数据采集，在整个屈伸弧中进行被动运动。在腕关节中立位时施加内翻和外翻重力应力。模拟了外侧副韧带重建。我们评估了桡骨小头切除和重建后，在存在横向骨折（Regan 和 Morrey 2 型）或固定冠状突的情况下，单极或双极植入物的不稳定性。
在存在外侧副韧带完整性的情况下，在外翻应力下，两种植入物的外翻松弛度没有差异（p=1.0）。当冠状突骨折时，每种假体的松弛度改善都更高（单极：7.4°±1.6°，p<0.001；双极：6.4°±1.6°，p=0.003），而当冠状突固定时则更低（单极：4.0°±1.6°，p=0.02；双极：4.2°±1.6°，p=0.01）。在可用的数量下，在外翻应力下，两种植入物的外旋松弛度没有差异（p=1.0）。假体的最大稳定效果发生在冠状突骨折时（单极：3.3°±1.2°，p=0.15；双极：3.3°±1.2°，p=0.17）。桡骨小头置换术在存在外翻或内旋松弛的情况下，对内侧副韧带重建的三联征尸体模型中的内翻应力没有提供实质性的稳定性。
在我们的三联征尸体模型中，冠状突固定可有效改善单极或双极假体放置时的内翻松弛度。此外，无论冠状突状态如何，两种类型的假体都能有效改善肘关节的外翻和外旋松弛度。如果外侧副韧带完整或重建，我们的尸体模型数据支持在三联征损伤中使用这两种植入物类型。
如果外侧副韧带完整或重建，我们的尸体模型数据支持在三联征损伤中使用这两种植入物类型。
